C4 plants produce this 4 carbon compound (oxaloacetate) to increase their photosynthetic efficiency. C4 plants have a unique leaf anatomy with bundle sheath cells around the vascular bundle. In the bundle sheath cells are found chloroplasts where the majority of carbon fixation occurs. The bundle sheaths confer increase in photosynthetic efficiency because they are away from the surface of the leaf and therefore away from high atmospheric oxygen concentrations and sunlight which would lead to photorespiration, an energy costly process. Bundle sheaths also allow for quick transport of produced sugars to vascular bundle. So, C4 plants need to produce oxaloacetate to transport assimilated carbon to the bundle sheath cells. C4 plants spatially separate carbon fixation while CAM plants temporally separate.
As for pyruvate vs pyruvic acid, in organic chemistry the suffixes -ate and -ic acid refer to either presence or absence of a proton. pyruvate is the deprotonated anionic analog of pyruvic acid.
funktion,
So essentially these bundle sheath cells in C4 plants do the carbon fixing by taking CO2 from the atmosphere and making it into oxaloacetate which later gets broken down to CO2 again for the Calvin cycle, right? Isn't oxaloacetate the 4 carbon compound the one that joins with acetyl CoA to form citric acid in Kreb's cycle as well?
But then following what osimsdds says, the 4 carbon compound is malate, right? So, which one is true? Oxaloacetate or Malate? I am a little confused about what osimsdds is saying.
As far as what I have studied, photorespiration is the ability of C3 plants in being able to keep its stomata closed in hot and dry weather while still being able to continue the "show" with the accumulating byproduct of O2 already within the plant. When stomata is closed, there is no intake of CO2, so C3 plants use photorespiration by inserting O2 into Calvin cycle to produce PGAL- the precursor of sugars.
C4 plants have an adaptation which enables the plant to grab ahold of CO2 without opening its stomata. The C4 plant has a special enzyme, which according to osimsdds is "PEP" that has a strong affinity for CO2, which I am deducing- happens in the bundle sheath cells as funktion has mentioned. So in all, C4 is able to insert CO2 into Calvin cycle to produce PGAL whereas C3 plants insert O2.
As for CAM plants, they are similar to C4 plants in that the plant stores CO2 in a 4 carbon format (oxaloacetate or malate-still confused on this part) by grabbing ahold of CO2 from the atmosphere at night (opening its stomata when it is cooler) and storing it till day when the 4 carbon compound is broken down and CO2 is introduced into the Calvin cycle.
With funktion and osimsdds's inputs, this is how I understand the processes. If there is anything flawed and incorrect, please feel free to correct for I just want to get it right.
My knowledge comes from Schuam's Bio and Campbell/Reece.
Thanks for your help guys, 9 days till judgement day!
